Methods of fabricating aircraft skis and components thereof



Nov. 22, 1960 w. K. LANDES METHODS OF FABRICATING AIRCRAFT SKIS ANDCOMPONENTS THEREOF Original Filed June 14, 1955 IN V EN TOR. Ives/eAfLmdes HTTORNEYS BLMMW unit d S a Pitchfo- METHODS OF FABRICATINGAIRCRAFT AND COMPONENTS THEREOF Wesley K. Landes, Box 15Z, Anchorage,Alaska Original application June 14, 1955, Ser. No. 515,377. Divided andthis application June 12, 1959, Ser. No. 820,569 a Y 4 Claims. (Cl.154-110) The present invention relates to vehicular skis, and moreparticularly relates to vehicular skis for use on aircraft and the like,wherein improved operational characteristics are achieved by'uniqueconstructional features including a hollow pedestal and runner surfaceintegrally fabricated from high strength, light-weight material such ashardenable synthetic resin impregnatedfwithglass fibers, and furtherrelates particularly to methods of manufacturing such skis.

' Heretofore, known vehicular skis of the type employed on aircraft andthe like under conditions where the landing areas are covered with snowand/or ice have been constructed of wood or metal or combinationsthereof. Such aircraft skis customarily use a generally transverselyflat wood runner to provide the runner surface, with metal being usedfor the snow contacting surface in many instances, and withmetal alsobeing used in certain designs to provide a stiff pedestal or bracingstructure between the runner surface and the associated axle of theaircraft landing gear. Additional, certain more recently developedconventional aircraft skis are constructedentirely of metal.

Difliculty is encountered in achieving the requisite runner strength andresiliency when wooden runners are employed, particularlyundertconditions of extreme cold. The natural tendency of the woodenrunner to absorb moisture, which then becomes frozen in the grain of thewood and produces brittleness, presents a dangerous operational hazard,particularly in the bush-type operation commonly necessary in arcticandsub-arctic areas. Also,

prior types of skis having a wooden. runner and an at tached sheet metalrunner surface require frequent replacement and exhibit a dangeroustendency to become torn by sharp obstacles in a landing area, whichtendency is effectively minimized by use of the material andconstruction provided according to the present invention. Because ofthis tendency for the moisture content of a Wooden ski to freeze, andbecause o f-'the low thermal insulation qualities of metal runnersurfaces, both such types of conventional skis in addition develop amarked tendency to stick orfreeze in mice or show while the aircraft isstanding or maneuvering onthe landing area. Such hazard and limitationon the maneuverability of an aircraft can be of serious consequence inremote areas.

When fabricated entirely of metal or from a combination of wood andmetal, certain disadvantages have been encountered in such skis ofconventional design, since the use ofmetal tends to render the skisunduly heavyand to reduce the aircraft pay load. Further, and moreimportantly from the point of view of operational safety, skisfabricated from metal or a combination of Wood and metal arecharacterized by stiffness and rigidity, and consequently require thatsubstantially all of the shock of landing be absorbed by the landinggear struts of the aircraft. Aircraft landing gear by standardizeddesign is intended primarily for use with wheels mounting pneumatictires. When a rigid type of ski is substituted for a pneuinatic tiremounting wheel, the absence of a degree an improved ski for use onaircraft and the like which A of shock cushioning action in the skiwhich is comparable to the cushioning action of a pneumatic tirenecessarily increases the probability of failure of the landing gearunder conditions of severe shock. I j p A primary object of the presentinvention is to provide eliminates or in large measure effectivelyminimizes the difficulties heretofore encountered in operating underconditions of severe cold, where use of wood or metal or combinationsthereof has heretofore necessarily involved adoption of one or moreundesirable characteristics such as undue increase in weight andstiffness, insufiicient strength, a marked tendency to brittleness insevere cold,

and/or sticking characteristics adversely affecting the maneuverabilityof the aircraft on the landing surface.

One object of the present invention is to provide anaircraft ski ofmaterialy reduced weight per given strength.

'.A further object of the presentinvention is to provide anaircraft-type ski of integrally bonded construction capable ofsufficient strength to resist downward, transverse, and twistingstresses and strains exceeding strength requirements set forth by theCivil Aeronautics Administration, which ski is materially lighter andmore durable than any.' conventional ski meeting comparablerequirements.

Another object of the present invention is to provide an aircraft skihaving an improved degree of freedom from rough surfaces, thus providinga ski with superior airflow characteristics, i.e. which is moreaerodynamically clean, in flight.

A further object of the present invention is to provide an aircraft skiimpervious to the penetration of moisture and requiring, forall-practical purposes, no maintenance. Another and related object ofthe present invention resides in provision for an aircraft skiimpervious to the penetration of moistureand also having superiorqualities of thermal insulation under conditions of severe cold, thusmaterially reducing any tendency for the ski to stick to supporting iceor snow while being maneuvered or stored under conditions of extremecold. A further related ob ject and advantage of the present inventionis to provide an aircraft ski exhibiting the quality of maintainingrequisite flexibility,'i.e. no tendency toward brittleness, und'erconditions of severe cold.

The further and more specific object of the present of to permit boththe pedestal portion and runner portion of the ski to fiex under shock.A related and more specific advantage of the present'inventionis foundin provision for a slopingpedestal portion extending from the axlebearingand diverging longitudinally of the ski a major portion of thelongitudinal dimension thereof and a major portion of the transversedimension thereof, to provide an enhanced cushioning effect between theaxle bearing and the runner surface, and to provide increased strengthper given weight under conditions of stress. A further related object ofthe present invention resides in providing a generally fiat pedestalportion on theupper surface of said ski, extending from saidsloping-pedestal portion in directions generally parallel to and spacedfrom the adjacent runner surface, which generally flat pedestal portionis integrally joined to said runner surface only adjacent the edgesthereof, thus imparting further resiliency and strength to the ski.

An additional object of the present invention resides in provision in anaircraft-ski of means for connecting Patented Nov. 22,

the runner surface to the axle bearing mounting pedestal portion of theski only adjacent the edges thereof to provide a hollow core orinterspace between said pedestal portion and said runner surface, and aresilient, unsupported, longitudinally extending runner central portionexhibiting the characteristic of assuming a transversely concavedconfiguration when supporting considerable load, as during the initialstages of landing, such configuration providing a materially improveddegree of directional stability during this critical initial stage ofcontact of the aircraft with a landing surface. A related additionalobject of the present invention is found in the dynamic nature of theaforementioned transversely concave configuration of the runner surfaceof an aircraft ski, according to the present invention, in that underconditions of primarily static load, such concave configurationdisappears and accordingly does not interfere with maneuverability ofthe aircraft on the landing surface after landing.

Yet another object of the present invention is to provide an improvedmethod of fabricating an integral ski for use on aircraft and the like,wherein successive layers of a hardenable synthetic resin and highstrength reinforcing fibers are built up in a depression-type moldandbonded integrally to a runner surface layer in a manner leaving a hollowcore or enclosed interspace therebetween. A related object of thepresent invention involves a method of pigmenting the exterior surfaceof such a ski in a manner advantageously facilitating removal of theformed pedestal portion of the ski from the mold forming the same.

In its more general aspects, the present invention involves an aircraftski of integral construction, the runner surface layer of the ski beingbonded to the axle bearing mounting pedestal portion of the ski onlyadjacent the edges thereof to provide what may be termed a hollow coreor enclosed interspace. More specifically, the present inventionutilizes as the essential material for fabrication of the ski a moistureimpervious, high strength, light weight material such as a hardenablesynthetic resin advantageously having impregnated therein woven highstrength glass fibers.

It has been found that such resinous material advantageously havingimpregnated therein such high strength fibers, provides the necessarystrength, lightness in weight, flexibility, moisture imperviousness, andother desirable low temperature characteristics rendering use thereofreniarkably superior in aircraft skis when constructed in the mannerprovided by the present invention.

The above and other objects and advantages of the present invention willbe apparent from the following description of a typical example thereof,set forth by way of illustration and not limitation, wherein likenumerals refer to like parts and wherein:

Figure 1 is a top plan view of an illustrative embodiment of the presentinvention;

Fig. 2 is a view in side elevation of the ski as illustrated in Figure1, taken along line 2-2 thereof;

Fig. 3 is a longitudinal cross-section of the ski as illustrated inFigure 1, taken along line 3-3 thereof;

Fig. 4 is a transverse cross-section of the ski las illus trated in Fig.2, taken along line 4-4 thereof;

Fig. 5 is a transverse cross-section of the ski as illustrated in Fig.2, taken along line 5--5 thereof;

Fig. 5A is a view corresponding to Fig. 5, showing the concavetransverse configuration of the ski runner when under dynamic load, asduring the initial stages of landing;

Fig. 6 is a transverse cross-section of the ski as illustrated in Fig.2, taken along line 66 thereof; and

Fig. 7 is a transverse cross-section of the ski as illustrated in Fig.2, taken along line 7-7 thereof.

Considering the above illustration of the present invention in greaterdetail, the top or pedestal of the ski comprising longitudinallyextending sloping pedestal portions 10 and 11, transversely extendingsloping pedestal portions 12 and 13', agenerally flat' pedstal'portion14 extending generally parallel tdf runner surface 15, and pedestal edgeportion 16, is first fabricated in a depression type mold, not shown(the mold configuration being considered apparent from the formedpedestal configuration), by successive build-up of an appropriate numberof layers of a hardenable synthetic resin and woven glass fibers. i i

More specifically, the mold for the pedestal portion is first preparedin a generally conventional manner by waxing the surface thereof andspray-coating thereon a parting or release'agent 'such as polyvinylalcohol, the purpose of the latter being to facilitate the subsequentremoval of the fabricated pedestal portion from the pedestal mold.Applied next to the mold surface is what may be termed a gel-coat,"which is a pigmented plastic in liquid form, to provide the appropriateexternal coloring to the fabricated ski and also provide protection forthe wax and release agent applied to the mold surface, preventing attackthereof by the subsequent curing reaction of the hardenable syntheticresin formed in the mold, as hereinafter more fully set forth. After thegel-coat has set, a layer of hardenable syntheticresin in liquid form,such as a polyester suitably catalyzed to cure at room temperature, isapplied to the gel-coat, which layer of resinous material is followed bya layer of woven glass fibers, the layers of resinous material and wovenglass fibers being applied alternately to build up the appropriatepedestal construction along the external configuration thereof, theappropriate thickness dimensions of which will be more apparent from thetypical dimensions hereinafter set forth by way of example. As thepedestal portion of the ski is completed and becomes set, it is removedfrom the pedestal mold and a hole is drilled through each of the uppertransverse sides of the central pyramidal portion thereof to accommodatethe axle bearing 17. Axle bearing 17, which is desirably of hardenedchrome-molyb' denum alloy construction, is provided with a protectivelayer of resinous material, advantageously an epoxy-type resin, toaccomplish a better bond of the metal surface of axle bearing 17 to theformed pedestal, which coating of resinous material has impregnatedtherein a layer of woven glass fibers. Following such preparation ofaxle bearing 17, the'axle bearing 17 is bonded to the pyramidal pedestalportion with the ends thereof extending through the holes provided insaid pyramidal pedestal portion, as by application of further layers ofepoxyor polyester type resin thereto. The interior portion of thepedestal adjacent the axle bearing 17 is thereupon further strengthenedby additional alternate layers of polyester-type hardenable syntheticresin and woven glass fibers to build up the thickness dimensions of thepedestal portions adjacent axle bearing 17 to the degree indicated inthe illustrated embodiment of the invention, as at wall portions 18, 19,20, 21, 22 and 23 (see Fig. 3).

Digressing to a consideration of the preparation of the surface ofpedestal outer edge 16 which is subsequently bonded to the runnersurface layer 15 of the ski, the surface of edge 16, after being builtup to the desired thickness but before final set, has a fine weave tapeimpressed in the tacky surface thereof. After hardening of the resin andremoval of the tape, a rough surface is presented to the subsequentlyapplied runner surface layer 15. Such roughening of the bonding surfaceof edge 16 promotes cohesion and bonding of the pedestal and runnersurface portions of the ski. The resulting bond is schematicallyindicated in dotted line at 24 on Figs. 2 through 7 for purposes ofillustration and description, it being understood that such mannerof'fabrication results in an integral bond between'said runner surface15 and the edge portion16o f the pedestal portion of the ski.

It will of coursebe also understood that the runner surface 15 of theski willbe suitably sloped upward 5. at the leading and trailing endsthereof, as is conventional in the art, and as indicated at respectivesloping portions 25 and 26, such configuration being accomplished bysuitable pedestal and runner surface mold design, as desired.

Fabrication of the runner surface layer 15 is desirably accomplished ona generally flat mold of configuration to mate with the pedestal portionand specifically contact edge area 16 thereof, and is built up fromsuccessive layers of a suitable hardenable synthetic resin, such as apolyester resin in liquid form which is suitably catalyzed to harden atnormal temperatures, such resinous material being applied in alternatelayers with layers of woven glass fibers to build up the runner surfacelayer thickness dimension intended. When such runner surface layerthickness dimension has been attained and while the last layer thereofis still moist, the edges thereof are applied to the roughened surfaceof the pedestal outer edge 16 and bonded thereto under pressure tointegrally form the complete ski. Finally, the lower exposed surface ofrunner 15 is sprayed with one or more coats of an epoxy-type resin, inthe typical example of the invention set forth, to impart theretogreatly improved antisticking properties under snow and ice conditions,it having been found that an epoxy-type resin surface is superior to apolyester-type resin surface in this regard.

In a constructed embodiment typifying the invention as illustrated, theoverall length is 72 inches and the overall width is inches, with a 1%inch outer diameter axle bearing installed in the pyramidal portion ofthe pedestal portion of the ski with its center 7% inches above therunner external surface. The axle bearing center line is situated 43 /2inches from the leading edge of the ski. Sloping pedestal portions 10and 11 respectively extend 32 inches and 19 inches measured horizontallyfrom the axle bearing axis, or about three-fourths of the overall skilength, and the configuration of generally flat pedestal portion 14provides that its external upper edge is spaced between /2 inch and inchfrom the runner surface layer. The bonded area 16 of the pedestalportion varies in width from about 1 /2 inches at the leading andtrailing edges of the ski to approximately /2 inch at the lateral edgesthereof adjacent the axle bearing. Thickness dimensions of the laminatedstructure in the pedestal portion are approximately 4 inch at pointsabout half way along sloping portions 10 and 11, such smaller dimensioncontinuing out to the edges of the pedestal portion. The thickness ofthe typical runner surface employed is approximately inch. Fabricated ofthe dimensions indicated, the ski weight is approximately pounds, whichfactor of lightness in weight presents at least about a 40% improvementover conventional skis of comparable strength characteristics and runnersurface area. A ski having the above dimensional features has been foundideally suited for use on aircraft weighing up to 1500 pounds, and doesnot show fracture or deformation under concentrated and distributed downloads of 8,000 pounds, and under 2200 pounds concentrated anddistributed side loads, all such tests being conducted with the axlebearing in fixed position. Increasing the ski width to 11 or 12 inchesand providing an increase of about 25% or 50% in the pedestal portionand runner surface thickness dimensions produces skis weighing about 18or 22 pounds, suited for use with 2000 pound or 2500 pound aircraft,respectively. As will be apparent, proportionate variations in thespecific dimensions and weights set forth readily provide skis ideallyadapted for use with heavier or lighter aircraft.

Load tests have also confirmed the dynamic feature of transverseconcavity of the ski under shock conditions. To test this feature,comminuted vermiculite (to simulate snow or ice) was mixed with acementitious material, and the ski was placed in a bed of such mixtureunder test load sufficient to simulate shock conditions for a periodpermitting the cementitious material in the vermiculite to set.Following removal of the ski from 'the hardened: supporting bed, apronounced raised portion was clearly apparent in the bed portion underthe central or unsupported portion of the ski runner surface.

A ski according to the present invention may be provided with generallyconventional metal eyelets, not

aircraft according to conventional procedure, with each ski of anassociated pair being mounted with its axlev bearing pivotally retainedon the associated axle depending from the aircraft landing gear, andwith the aforesaid eyelets being connected to the aircraft byconventional flexible cable means and safety cables to limit thearc ofmovement of the ski.

The ski pedestal configuration presented utilizes to best advantage suchinherent characteristics of strength and resiliency as are availablefrom resinous material of the types herein disclosed. The slopingpedestal portions 10' and 11 extending for the major portion of thelongitudinal dimension of the ski, and sloping portions 12 and 13extending from bearing 17 for a major portion of the transversedimension of the ski effectively distribute the landing shock of theaircraft from the axle bearing 17 to the runner surface 15 of the ski ina manner calculated to most evenly distribute the force of such shockover the longitudinal and transverse dimensions of the pedestal.

Further, the incorporation of a generally level pedestal portion 14extending to adjacent the edges of the runner surface layer 15 from saidsloping pedestal portions 10, 11, 12 and 13 provides further effectivedistribution of shock to the entire runnersurface. Self-evident also isthe fact that the bonding of the'runner surface layer 15 with thepedestal edge portion 16 extending from pedestal portion 14 provides, asmore particularly shown in the cross-sectional views of Figs. 4 through7, that the longitudinally extending central portion of runner 15 isunsupported by virtue of the resulting hollow core or interspace 29 andmay flex under shock to provide a transverse concavity of the runnersurface, or what may be termed a hollow-ground effect, as typicallyshown in Fig. 5A, to further cushion landing shocks and provide amaterial degree of directional stability during initial stages oflanding of the aircraft, such action occurring when such directionalstability is often most critical to landing safety. Further,notwithstanding the dynamic character of the flexing or transverseconcavity so occasioned in runner surface 15, an airplane skiconstructed according to the present invention is possessed ofsufficient rigidity to provide an essentially flat runner surface underconditions of static load, thus not presenting the disadvantages of apermanently concaved runner surface in terms of ease of maneuverabilityon the landing surface during field maneuvering or storage.

It will be readily understood that a number of variations in the mannerof fabrication, types of laminating materials, and in the specificdimensional consideration employed, may be undertaken within the scopeof the present invention. By way of further example and not limitationin this regard, it is to be noted that other suitable hardenablesynthetic resins other than a polymerizable unsaturated polyester-typeresin may be employed, such as a polymerizable epoxy-type esterthroughout, or such cross-linking condensation-type resins or mixturesthereof as are compatible with the strength and resiliency for thepurposes indicated which may be utilized. Further, it will be understoodthat the high strength woven laminating material such as the woven glassfiber indicated by way of example, may have such other weave or otherarrangement of the material as may be desired. Thus, in certain designsadvantages will be found in uti lizing glass fiber laminating layershaving directional strength characteristics. Further variations in skidimensions, laminating and bonding materials, and fabrication procedureswill be apparent to those skilled in the art.

This application is a division of my copending application Serial No.515,377, entitled Ski for Aircraft and the Like, filed June 14, 1955,which is now US. Patent No. 2,950,883.

What is claimed is:

l. The method of fabricating a ski of laminated integral constructionfor use on aircraft and the like, comprising forming a pedestal portionfrom successive layers of a hardenable synthetic resin and woven glassfibers to provide a pedestal configuration having a centrally arrangedpyramidal area and sloping pedestal portions diverging therefrom,bonding a metal axle bearing to said pyramidal pedestal portion with theends of said bearing extending therethrough, forming a generally fiatrunner surface from successive layers of a hardenable synthetic resinand woven glass fibers, and bonding said pedestal portion and saidrunner surface only adjacent the edges thereof to provide an integralski construction enclosing a hollow interspace between said pedestalportion and said runner surface, said interspace thereby extendingalmost the entire length and width of said ski in further providingenhanced strength and resiliency characteristic to a ski so formed.

2. The method of fabricating a ski for use on aircraft and the like,comprising forming a depression mold conforming to the desired externalpedestal configuration, successively applying a hardenable syntheticresin in liquid form and layers of woven glass fibers to build upappropriate pedestal thickness dimensions, curing the resultinglaminate,bonding a metal axle bearing in a position extending throughsaid pedestal portion, forming 8 a laminatedrunner surface fromsuccessive layers of said resinous material and woven glass fibers, andpressure bonding said runner surface while still moist to the outeredges of said pedestal portion.

3, The method according to claim 2, wherein said hardenable syntheticresin is catalyzed to polymerize at normal temperatures.

4. The method of fabricating a ski for use on aircraft and the like,comprising forming a depression mold conforming to the desired externalpedestal configuration, waxing the surface of said mold, spray-coatingthereon a release agent, applying to the mold surface a pigmentedplastic in liquid form to provide appropriate external coloring to thefabricated ski and also provide protection for the wax and release agentapplied to the mold surface from attack by the subsequent resin curingreaction, successively applying a hardenable synthetic resin in liquidform and layers of woven glass fibers to build up appropriate pedestalthickness dimensions, curing the resulting laminate, toughening theouter edge of the pedestal portion so formed, drilling a hole througheach of the upper transverse sides of the central portion of saidpedestal portion to accommodate an axle bearing, securely bonding anaxle bearing in a position extending through said pedestal portion,forming a laminated runner surface layer from successive layers of saidresinous material and woven glass fibers, pressure bonding the outeredges of said runner surface while still moist to the outer edges ofsaid pedestal portion, and applying a coating of epoxytype resin to theexternal surface of said runner.

No references cited.

1. THE METHOD OF FABRICATING A SKI OF LAMINATED INTEGRAL CONSTRUCTIONFOR USE ON AIRCRAFT AND THE LIKE, COMPRISING FORMING A PEDESTAL PORTIONFROM SUCCESSIVE LAYERS OF A HARDENABLE SYNTHETIC RESIN AND WOVEN GLASSFIBERS TO PROVIDE A PEDESTAL CONFIGURATION HAVING A CENTRALLY ARRANGEDPYRAMIDAL AREA AND SLOPING PEDESTAL PORTIONS DIVERGING THEREFROM,BONDING A METAL AXLE BEARING TO SAID PYRAMIDAL PEDESTAL PORTION WITH THEENDS OF SAID BEARING EXTENDING THERETHROUGH, FORMING A GENERALLY FLATRUNNER SURFACE FROM SUCCESSIVE LAYERS OF A HARDENABLE SYNTHETIC RESINAND WOVEN GLASS FIBERS, AND BONDING SAID PEDESTAL PORTION AND SAIDRUNNER SURFACE ONLY ADJACENT THE EDGES THEREOF TO PROVIDE AN INTEGRALSKI CONSTRUCTION ENCLOSING A HOLLOW INTERSPACE BETWEEN SAID PEDESTALPORTION AND SAID RUNNER SURFACE, SAID INTERSPACE THEREBY EXTENDINGALMOST THE ENTIRE LENGTH AND WIDTH OF SAID SKI IN FURTHER PROVIDINGENHANCED STRENGTH AND RESILIENCY CHARACTERISTIC TO A SKI SO FORMED.